Methods of making paper tissue, towel, and the like, are well known, including using various features such as Yankee drying, through-air drying, fabric creping, dry creping, wet creping, and so forth. Conventional wet pressing (CWP) processes have certain advantages over conventional through-air drying processes including: (1) lower energy costs associated with the mechanical removal of water than transpiration drying with hot air and (2) higher production speeds that are more readily achieved with processes that utilize wet pressing to form a web. On the other hand, through-air drying processing has been adopted for new capital investment, particularly, for the production of soft, bulky, premium quality tissue and towel products.
Fabric-creping has been employed in connection with papermaking processes that include mechanical or compactive dewatering of a paper web as a means to influence product properties. See U.S. Pat. Nos. 4,689,119, and 4,551,199 of Weldon; U.S. Pat. Nos. 4,849,054 and 4,834,838 of Klowak; and U.S. Pat. No. 6,287,426 of Edwards et al. While, in many respects, these processes have more potential than conventional papermaking processes in terms of energy consumption and the ability to use recycle fiber, operation of fabric-creping processes has been hampered by the difficulty of effectively transferring a web of high or intermediate consistency to a dryer. Note also, U.S. Pat. No. 6,350,349 to Hermans et al., which discloses wet transfer of a web from a rotating transfer surface to a fabric. Further U.S. patents more generally relating to fabric-creping include the following: U.S. Pat. Nos. 4,834,838; 4,482,429; 4,448,638, as well as U.S. Pat. No. 4,440,597 to Wells et al.
In connection with papermaking processes, fabric molding has also been employed as a means to provide texture and bulk. In this respect, there is seen, in U.S. Pat. No. 6,610,173 to Lindsay et al., a method for imprinting a paper web during a wet pressing event that results in asymmetrical protrusions corresponding to the deflection conduits of a deflection member. The '173 patent reports that a differential velocity transfer during a pressing event serves to improve the molding and imprinting of a web with a deflection member. The tissue webs produced are reported as having particular sets of physical and geometrical properties, such as a pattern densified network and a repeating pattern of protrusions having asymmetrical structures. With respect to wet-molding of a web using textured fabrics, see, also, the following U.S. Pat. Nos. 6,017,417 and 5,672,248 both to Wendt et al.; Nos. 5,508,818 and 5,510,002 to Hermans et al. and No. 4,637,859 to Trokhan. With respect to the use of fabrics used to impart texture to a mostly dry sheet, see U.S. Pat. No. 6,585,855 to Drew et al., as well as United States Patent Application Publication No. 2003/0000664, now U.S. Pat. No. 6,607,638.
Through-air dried, creped products are disclosed in the following patents: U.S. Pat. No. 3,994,771 to Morgan, Jr. et al.; U.S. Pat. No. 4,102,737 to Morton; and U.S. Pat. No. 4,529,480 to Trokhan. The processes described in these patents comprise, very generally, forming a web on a foraminous support, thermally pre-drying the web, applying the web to a Yankee dryer with a nip defined, in part, by an impression fabric, and creping the product from the Yankee dryer. A relatively permeable web is typically required, making it difficult to employ recycle furnish at levels that may be desired. Transfer to the Yankee dryer typically takes place at web consistencies of from about 60% to about 70%.
As noted in the above, through-air dried products tend to exhibit enhanced bulk and softness. Thermal dewatering with hot air, however, tends to be energy intensive. Wet-press operations wherein the webs are mechanically dewatered are preferable from an energy perspective and are more readily applied to furnishes containing recycle fiber, which tends to form webs with less permeability than virgin fiber. Many improvements relate to increasing the bulk and absorbency of compactively dewatered products that are typically dewatered, in part, with a papermaking felt.
U.S. Pat. No. 5,851,353 to Fiscus et al. teaches a method for can drying wet webs for tissue products wherein a partially dewatered wet web is restrained between a pair of molding fabrics. The restrained wet web is processed over a plurality of can dryers, for example, from a consistency of about 40 percent to a consistency of at least about 70 percent. The sheet molding fabrics protect the web from direct contact with the can dryers and impart an impression on the web. See also U.S. Pat. No. 5,336,373 to Scattolino et al.
Despite advances in the art, existing wet press processes have not produced highly absorbent webs with preferred physical properties, especially, elevated cross machine direction (CD) stretch at a relatively low machine direction to cross machine direction (MD/CD) tensile ratios as are sought after for use in premium tissue and towel products.
In accordance with the present invention, the absorbency, bulk and stretch of a wet-pressed web can be vastly improved by wet fabric creping a web and rearranging the fiber on a creping fabric, while preserving the high speed, thermal efficiency, and furnish tolerance to recycle fiber of conventional wet press processes. The inventive process has the further advantage that existing equipment and facilities can readily be modified to practice the inventive process, using, for example, can dryers that are particularly amenable to recycle energy sources and/or lower grade, less expensive fuels that may be available.